Science Reviewer: Earthquakes and Faults PDF

Science reviewer What is an earthquake? - An **earthquake** is the shaking movement of the ground caused by a sudden shift or slip on a fault. What is a fault? - A **fault** is a break in the rocks that make up the earth's crust. What causes Earthquake? 1. The tectonic plates are alwa...

Science reviewer What is an earthquake? - An **earthquake** is the shaking movement of the ground caused by a sudden shift or slip on a fault. What is a fault? - A **fault** is a break in the rocks that make up the earth's crust. What causes Earthquake? 1. The tectonic plates are always moving but they stuck at their edges due to friction. 2. When the stress on the edge of the tectonic plates overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth\'s crust and cause the shaking that you feel. Types of Faults: 1. **Normal Fault-**is a dip-slip fault formed by ***tensional stress*** where hanging wall moves down relative to the footwall. 2. **reverse fault-**is **dip-slip fault** formed by ***Compressional stress*** where hanging wall moves up relative to the footwall (vertical). 3. **strike-slip fault-**is formed by **shear stress** where sides slide past each other (horizontal). **Where are faults formed?** - Faults are formed along plate boundaries. - Normal faults are formed along **divergent boundaries** - Reverse faults are formed along **convergent boundaries** - Strike slip faults are formed along **sliding/transform boundaries**. +-------------+-------------+-------------+-------------+-------------+ | Type of | **Type of | **Type of | **Fault | **Type of | | Fault | Stress that | Fault** | Diagram** | Boundary | | | Causes | | | (where can | | | Fault | **Movement* | | it be | | | formation** | * | | formed)** | +=============+=============+=============+=============+=============+ | Normal | TENSIONAL | VERTICAL | | DIVERGENT | | Fault | STRESS | | | | | | | (HANGING | | | | | | WALL | | | | | | | | | | | | MOVES DOWN) | | | +-------------+-------------+-------------+-------------+-------------+ | Reverse | COMPRESSION | VERTICAL |  | | | | STRESS | (HANGING | | | | | | | | | | | | WALL MOVES | | | | | | UP) | | | +-------------+-------------+-------------+-------------+-------------+ | Strike-Slip | SHEAR | HORIZONTAL | | TRANSFORM | | fault | STRESS | | | | | | | /SLIDING | | | | | | PAST | | | | | | | | | | | | EACH OTHER) | | | +-------------+-------------+-------------+-------------+-------------+ **Landforms that the fault forms** ------------------------------------  VALLEYS  MOUNTAINS  RIDGES Describe **focus** of an earthquake? - Earthquake is the shaking of the earth's surface which is usually caused by the release of energy from the interior part of the earth. - The spot in the interior part of the earth where earthquake originates is called the **focus.** Describe **epicenter** of an earthquake - The spot on the surface of the earth just above the focus is called the **epicenter** of the earthquake. - - An earthquake maybe described as to how strong or weak is its vibration. - The strength of an earthquake can be described on the basis of the energy released by the Earth which can be calculated by scientists. - The strength of its vibration can be observed through its effects in the surrounding. Magnitude and Intensity - The **magnitude** of an earthquake is a measure of the energy release at the source. - **Intensity** measures the strength of shaking produced by the earthquake as observed by the people at certain location. Measuring Earthquakes -. Magnitude of Earthquake- the amount of energy released during an EQ - Richter Scale- based on the largest seismic waves generated by the EQ on a factor of 10 (magnitude 2 is 10x stronger than magnitude 1). - Moment Magnitude Scale- considers the size of the fault rupture, the amount of movement, and rock's stiffness - Magnitude of earthquake is expressed in Hindu-Arabic numerals as in 1,2,3,....10 - Magnitude 2 may or may not be felt - Magnitude 4 can be felt - Magnitude 6 can lead to a lot of damage in populated areas - Magnitude 7 can cause severe damage. - Magnitude 8 or 9 results in widespread destruction esp. near the epicenter - 2\. Intensity of Earthquake -- determined by observing the effects such as extent of damage of properties (buildings, houses, other structures, loss of lives) Intensity is expressed in Roman Numeral such as I, II, III,.....X The farther the place from the epicenter, the lesser is the intensity Factors Affecting Intensity: - 1\. Nature of the ground - a\. igneous and metamorphic rocks -- strong ground - b\. sedimentary rocks -- weak, loose ground 2\. Design of the building Active and inactive faults: - **Active faults** are those that show movement in the recent decades and can become a source of another earthquake in the near future. - **Inactive faults** are identified narrow zones but do not have records of movement for the past centuries. The three main layers of earth: - **crust, mantle**, and **core**. - The **crust** is the outermost layer, hard and brittle (made up of rocks and minerals) and has a thickness of 40 km. It is where buildings, houses and living things are found. - The **mantle** is the second layer and the thickest layer. - It makes up 84% of the earth's volume, semi-solid and dense. - It has a thickness of 2,900 km from the crust. - Its temperature is between 2,200 ^0^C to 3, 700 ^0^C - the outer core - the inner core - The **outer core** is made of molten, liquid iron and nickel. - It is 2300 km in thickness and has a temperature between 4000 ^0^C to 5000 ^0^C - The **inner core** is made up of solid iron and nickel. - It is 1200 km in thickness and its temperature is between 5000 ^0^C to 7000 ^0^C. - When an earthquake occurs the **seismic waves** (P and S waves) are produced and they all move in different ways through the Earth\'s layers. - Seismic waves are vibrations that travel through the Earth carrying the energy released during earthquakes - Seismic waves travel fastest through solid than liquid. - Seismic waves slows down in hot areas such as in molten areas within the Earth. - Seismic stations record seismic waves that have traveled though Earth's layers and are installed or placed at increasing distances from the earthquake epicenter. 2 Types of Surface Waves - Rayleigh wave - surface wave causing the ground to shake in an elliptical motion - Because of its motion, it moves the ground up and down, and side-to-side in the same direction that the wave is moving - Most of earthquake shaking is due to this type of wave - Love wave- produce entirely horizontal motion - Moves the ground side-to-side - Named after A.E.H. Love a British mathematician Two types of body waves: - Primary (P) wave - Secondary (S) wave P waves- are the first waves to arrive at a seismograph station. -fastest form of wave, sometimes called compression waves. - Can move through both liquids and solids (can travel in core, mantle & crust) - These waves cause rock particles to move back and forth in the same direction as the wave is traveling (push-pull). S-Waves- arrive after the primary waves at the seismograph station. -Can travel through solids only as tranverse wave (mantle & crust only). -Cause particles to move back and forth at right angles to the line of wave movement - According to the **Philippine Atmospheric, Geophysical, and Astronomical Services Administration** (PAGASA), about 20 tropical cyclones enter the Philippine Area of Responsibility (PAR) each year. - Typhoons are like giant engines that use warm, moist air as fuel. - This is the reason why typhoons form only over warm ocean waters near the equator. - In the north-eastern part of the Pacific Ocean and in the northern part of the Atlantic Ocean, the equivalent term is hurricane. - In Indian Ocean, they are called cyclones. - The only difference among the 3 is the location where the storm occurs. - Condensation follows, forming a band of clouds. The whole system of clouds and wind movements depend on the ocean's heat and water evaporating from the surface. - Density is they key factor behind the upward motion of warm air. Compared to cold air, warm air is less dense causing it to rise. - Why do typhoons mostly form in oceans near equator? - Low Pressure Area (LPA) -- a region where the atmospheric pressure is lower than that of surrounding locations. Winds blow towards the low pressure and the air rises in the atmosphere where they meet. As the air rises, the water vapor within it condenses, forming clouds and often rain. - **The Philippine Archipelago is situated between Taiwan and Borneo, with the waters of the Pacific Ocean and China Sea washing its coastline.** - **Due to its geographical location, the Pacific Typhoon Belt, cyclonic storms and floods have been the principal natural hazard in the Philippines-based on frequency of occurrence and scale of intensity.**  PAGASA - At the eye of a tropical cyclone, wind speed is low. At the eyewall, the wind speed is great. When the eye of a tropical cyclone passes over a certain place, it is the winds at the eyewall that wreak a lot of damage. Comets: - A comet is a small body of ice, rock and cosmic dust loosely packed together. - Scientists refer to them as dirty snowballs. Comets Orbit: - Comets orbit the Sun in highly elliptical orbits. - Their velocity increases greatly when they are near the Sun and slows down at the far reaches of the orbit. - Since the comet is light only when it is near the Sun (and is it vaporizing), comets are dark (virtually invisible) throughout most of their orbit. - The solar wind pushes the tail away from the Sun.  - When they are near the [Sun](http://www.nineplanets.org/sol.html) and active, comets have several distinct parts: Remember: - A comets ion tail always points away from the sun. - Solar winds blow the ion tail away from the sun. - Scientists believe that long period comets come from the Oort Cloud, a region that surrounds the solar system. - Short period comets can also come from the Kuiper Belt which exists outside of Neptune's orbit. Halleys Comet: - Halley\'s returns to the [inner Solar System](http://en.wikipedia.org/wiki/Inner_Solar_System) have been observed and recorded by [astronomers](http://en.wikipedia.org/wiki/Astronomers) since at least 240 [BCE](http://en.wikipedia.org/wiki/BCE). - Clear records of the comet\'s appearances were made by [Chinese](http://en.wikipedia.org/wiki/Chinese_people), [Babylonian](http://en.wikipedia.org/wiki/Babylonian), and [medieval European](http://en.wikipedia.org/wiki/Middle_Ages) [chroniclers](http://en.wikipedia.org/wiki/Chroniclers), but were not recognized as reappearances of the same object at the time. - The comet\'s periodicity was first determined in 1705 by [English](http://en.wikipedia.org/wiki/English_people) astronomer [Edmond Halley](http://en.wikipedia.org/wiki/Edmond_Halley), after whom it is now named. Halley\'s Comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061 Asteroids: - Asteroids are small rocky bodies that revolve around the sun. - They range in size from a few meters to more than 900 kilometers in diameter. - Asteroids have irregular shapes, but some are spherical, or round. **[Ceres: was an asteroid, now a dwarf planet]** - Meteoroids are small rocky bodies that travel through space. - A meteor is a bright streak that results from a meteoroid burning up in Earth's atmosphere, what we call shooting stars. - A meteorite is a meteoroid that reaches the Earth's surface without burning up. Three types of Meteorites - [Stony- Rocky material] - [Metallic- Iron and Nickel] - [Stony Metallic- Rocky material, iron and nickel]